1. Field of the Invention
This invention relates to decorative surface coverings, and more particularly to decorative floor and wall coverings. Still more particularly the invention relates to thermoplastic decorative floor and wall coverings having an embossed appearance achieved without the use of mechanical embossing.
2. Description of the Prior Art
There are a number of known processes for making embossed plastic sheets for floor and wall coverings and the like utilizing various chemical embossing techniques. For instance, U.S. Pat. No. 3,359,352--Powell et al. relates to a method for forming a resinous composition surface covering having a geometric decoration. This is accomplished by depositing a layer of fine granules of resinous composition on the surface of a base, heating to sinter the granules and form a porous layer, printing a design on the sintered layer with a printing composition which will penetrate into the porous composition and then, by heat with or without pressure, forming the printed porous layer into a non-porous layer containing an inlaid design. It is further disclosed that a textured or embossed product can be obtained by including with the granules a substance which on further treatment will create voids in the granular layer. Controlling the amount of printing composition to fill such voids controls the location and depth of the embossing.
U.S. Pat. No. 3,554,827--Yanagishi relates to the production of a decorative panel by defining a first desired design on a first surface of a sheet and then applying a polymerization retarding agent to the first surface to form a second desired design thereon. The first surfce is thereafter coated with a polymerizable resin that contracts when it is cured. The resin-coated sheet is then subjected to a polymerizing environment, such as a heated oven.
Those portions of the resin out of contact with the retarding agent cure first, and as these portions contract, the portions of the resin above the second design are stretched and thinned out. The thinned-out portions of the resin define the indented second design in the cured resin.
U.S. Pat. No. 3,428,471--Tuthill et al. relates to a method for manufacturing an embossed cellular resinous sheet by applying to the surface of a gelled foamable resinous layer having a blowing agent uniformly distributed therethrough, a barrier ink, and preferably other inks, to form a decorative pattern thereon. The entire printed surface of the resinous layer including the barrier ink is then overcoated with a second layer containing an activator for the blowing agent. After aging the product for a suitable period, a wear layer is applied and the product is heated under controlled conditions of time and temperature to fuse the resinous layers and decompose the blowing agent throughout those areas not covered by the barrier ink, thereby producing an embossed resinous surface wherein those areas of the surfce that have not had applied thereto the barrier ink are elevated with respect to other areas of the resinous surface that have been coated with the barrier ink.
U.S. Pat. No. 3,772,138--Witman contemplates imparting an embossed appearance to a thermoplastic sheet by blending a vinyl resin, a plasticizer for the resin, and a blowing agent which decomposes when heated at a temperature in the range above the glass transition temperature of the plasticized vinyl resin and below the decomposition temperature of the plasticized resin. The blend, normally in the form of a plastisol when made, is formed into a sheet. There is then applied to the sheet in predetermined pattern a barrier film, the barrier film being one which will prevent penetration into said sheet of an activator (to be subsequently applied) for reducing the decomposition temperature of the blowing agent in the sheet. There is subsequently applied over the entire surface of the sheet a liquid containing said activator in order that the activator will penetrate into the sheet and lower the decomposition temperature or accelerate the rate of decomposition of the blowing agent, or both, in those areas to which the barrier compound has not been applied. The system is then heated to decompose the blowing agent in those areas in which the blowing agent is in contact with the accelerator.
None of the foregoing processes, however, provides an embossed textured product having sharply defined lines of demarcation in the embossed areas. The process of the present invention, however, does supply a method for achieving excellent depth of relief in the embossed pattern of the product and as such constitutes an improvement over heretofore known chemical embossing techniques.